FreeBSD -- Multiple OpenSSL vulnerabilities

Details

VuXML ID

7b1a4a27-600a-11e6-a6c3-14dae9d210b8

Discovery

2016-03-10

Entry

2016-08-11

Problem Description:

A cross-protocol attack was discovered that could lead
to decryption of TLS sessions by using a server supporting
SSLv2 and EXPORT cipher suites as a Bleichenbacher RSA
padding oracle. Note that traffic between clients and
non-vulnerable servers can be decrypted provided another
server supporting SSLv2 and EXPORT ciphers (even with a
different protocol such as SMTP, IMAP or POP3) shares the
RSA keys of the non-vulnerable server. This vulnerability
is known as DROWN. [CVE-2016-0800]

A double free bug was discovered when OpenSSL parses
malformed DSA private keys and could lead to a DoS attack
or memory corruption for applications that receive DSA
private keys from untrusted sources. This scenario is
considered rare. [CVE-2016-0705]

The SRP user database lookup method SRP_VBASE_get_by_user
had confusing memory management semantics; the returned
pointer was sometimes newly allocated, and sometimes owned
by the callee. The calling code has no way of distinguishing
these two cases. [CVE-2016-0798]

In the BN_hex2bn function, the number of hex digits is
calculated using an int value |i|. Later |bn_expand| is
called with a value of |i * 4|. For large values of |i|
this can result in |bn_expand| not allocating any memory
because |i * 4| is negative. This can leave the internal
BIGNUM data field as NULL leading to a subsequent NULL
pointer dereference. For very large values of |i|, the
calculation |i * 4| could be a positive value smaller than
|i|. In this case memory is allocated to the internal BIGNUM
data field, but it is insufficiently sized leading to heap
corruption. A similar issue exists in BN_dec2bn. This could
have security consequences if BN_hex2bn/BN_dec2bn is ever
called by user applications with very large untrusted hex/dec
data. This is anticipated to be a rare occurrence.
[CVE-2016-0797]

The internal |fmtstr| function used in processing a "%s"
formatted string in the BIO_*printf functions could overflow
while calculating the length of a string and cause an
out-of-bounds read when printing very long strings.
[CVE-2016-0799]

A side-channel attack was found which makes use of
cache-bank conflicts on the Intel Sandy-Bridge microarchitecture
which could lead to the recovery of RSA keys. [CVE-2016-0702]

s2_srvr.c did not enforce that clear-key-length is 0 for
non-export ciphers. If clear-key bytes are present for these
ciphers, they displace encrypted-key bytes. [CVE-2016-0703]

Impact:

Servers that have SSLv2 protocol enabled are vulnerable
to the "DROWN" attack which allows a remote attacker to
fast attack many recorded TLS connections made to the server,
even when the client did not make any SSLv2 connections
themselves.

An attacker who can supply malformed DSA private keys
to OpenSSL applications may be able to cause memory corruption
which would lead to a Denial of Service condition.
[CVE-2016-0705]

An attacker connecting with an invalid username can cause
memory leak, which could eventually lead to a Denial of
Service condition. [CVE-2016-0798]

An attacker who can inject malformed data into an
application may be able to cause memory corruption which
would lead to a Denial of Service condition. [CVE-2016-0797,
CVE-2016-0799]

A local attacker who has control of code in a thread
running on the same hyper-threaded core as the victim thread
which is performing decryptions could recover RSA keys.
[CVE-2016-0702]

An eavesdropper who can intercept SSLv2 handshake can
conduct an efficient divide-and-conquer key recovery attack
and use the server as an oracle to determine the SSLv2
master-key, using only 16 connections to the server and
negligible computation. [CVE-2016-0703]

An attacker can use the Bleichenbacher oracle, which
enables more efficient variant of the DROWN attack.
[CVE-2016-0704]